ENERGY giant SSE saw more than £330 million wiped off its stock market worth last night after it warned its full-year results could be hit by the impact of lower wind-farm output and high wholesale gas prices in the first quarter.

Shares in Perth-based SSE, one of Scotland’s biggest companies by market value, dropped 2.35 per cent after it revealed an £80m hit to first-quarter operating profits compared with forecasts.

It came on the day shareholders voted to approve the proposed merger of the company’s retail division, SSE Energy Services, with npower, the retail wing of Innogy of Germany.

SSE’s results warning came on the day it reported a 320,000 drop in total customer numbers in the three months to June 30, compared with the same period last year.

Output from SSE’s onshore and offshore wind farms was 15 per cent lower than planned in the first quarter because of poorer-than-average wind conditions. At the same time, the temperature in the UK across the three months to June 30 was 1.5 degrees centigrade warmer than the 30-year average, leading domestic gas demand to be 10% lower than it anticipated.

Adding to a challenging opening quarter for the firm, SSE also cited the impact of “persistently high gas prices” on first-quarter trading. Total energy customer numbers for Great Britain and Ireland stood at 7.45 million at June 30, the company reported, compared with 7.77m on the June 30 last year. It reported a 230,000 fall in customers at the same stage last year.

SSE chief executive Alistair Phillips-Davies said: “This new financial year has so far been characterised by lower-than-expected output of renewable energy and persistently high gas prices, but looking ahead we are very focused on fulfilling our obligations to energy customers and delivering on our key priorities.”

The update comes after SSE announced a 6.7% hike in its average gas and electricity bills in May, equal to around £76 per year. The move, which came into effect on July 11 and affects 2.36 million customers, followed warnings from the Big Six energy companies that the UK Government’s plans to introduce a cap on standard variable tariffs, alongside wholesale power costs, would lead to price increases. As well as SSE, npower, EDF, British Gas and ScottishPower have all pushed though big price rises this year.

The UK Government said that its energy cap will protect millions of households from unfair price rises after it is introduced this winter. It declared consumers are a step closer to cheaper bills after legislation to cap poor value energy tariffs completed its passage through Parliament on Wednesday. Ministers say legislation to require energy watchdog Ofgem to cap standard variable and default energy tariffs will prevent consumers overpaying the Big Six energy suppliers, which the Competition and Markets Authority said amounts to an average of £1.4 billion a year.

SSE said that the 2.28m electricity and 1.53m gas accounts it has on standard variable tariffs could be affected by the cap.

Shareholders voted comprehensively in favour of two resolutions paving the way for the npower merger at a general meeting yesterday. Subject to regulatory approval, a new holding company will be created and listed on the main London market.

George Salmon at Hargreaves Lansdown said the cash savings arising from the merger should result in a healthy dividend. But he warned that “SSE isn’t quite the strong and stable enterprise it might seem”.

He said: “That’s because it’s struggling to generate high enough returns from its multi-billion pound investment programme. Profits look like coming in about £80m below forecast, as the unreliable British weather meant output from wind and hydro stations was below par.”

At the company’s AGM in Perth, chairman Richard Gillingwater saw nearly 7% of the voted shares poll against his re-election. All 19 resolutions were passed.

Shares in SSE closed down 32.5p at 1,352p.